The present invention relates to a plasma display panel (PDP) used in a display device and a method of making the panel.
High-definition, large-screen television (TV) receivers such as high-definition TV have widely been demanded. Cathode ray tubes (CRT) are more favorable in resolution and quality of images than plasma displays or liquid crystal displays but not in its depth or its weight particularly for a large-screen type, 40 inches or larger. The liquid crystal displays successfully have a low power consumption and accepts a low driving voltage, but hardly have a large screen size and a wide viewing angle. The screen size of plasma displays increases to a greater size as 40 inches (for example, in page 7 of xe2x80x9cFunctional Materialsxe2x80x9d, in Vol. 16, No. 2, February 1996).
A conventional plasma display panel (PDP) and a display apparatus with the PDP will be described with referring to FIGS. 7 to 10.
FIG. 7 is a partial cross sectional perspective view of an image display region of the PDP. FIG. 8 is a schematic plan view of the PDP with a front glass substrate removed, where display electrodes, display scan electrodes, and address electrode are illustrated not completely for ease of the description. An arrangement of the PDP will be explained referring to the drawings.
As shown in FIGS. 7 and 8, the PDP 100 includes a front glass substrate 101 and a back glass substrate 102 both made of boron-silicon-sodium glass by a floating method.
The front glass substrate 101 has N display electrodes 103 and N display scan electrodes 104(1) to 104(N) provided thereon. The display electrodes 103 and the display scan electrodes 104(1) to 104(N) are covered with a dielectric glass layer 103 and a protective layer 106 made of MgO, thus providing a front panel.
The back glass substrate 102 has M address electrodes 107(1) to 107(M) provided thereon. The address electrodes 107(1) to 107(M) are covered with a dielectric glass layer 108 and barriers 109. Phosphor layers 110R, 110G, and 110B are provided between the barriers 109, thus providing a back panel.
The front panel and the back panel are bonded to each other by an air-tight sealing layer 121 which extends along the edges of the panels for sealing. A discharging space 122 is developed between the front panel and the back panel, and is filled with discharge gas. The electrodes 103, 104(1) to 104(N), and 107(1) to 107(M) of the PDP are arranged in matrix pattern where a discharge cell is formed at each intersection between the scan electrode 104 and the address electrode 107.
The electrodes of the front panel may generally includes transparent electrodes 111 and silver electrodes 112 on the front glass substrate 101, or silver electrodes 113 on the front glass substrate 101 as shown in FIGS. 9A and 9B, respectively. The display apparatus having the PDP 100 of the above arrangement includes a driver 135 which includes a display driver 131, a display scan driver 132, and an address driver 133 which are connected to the corresponding electrodes of the PDP 100, and a controller 134 for controlling their operation. As being controlled by the controller 134, the drivers apply specific wave voltages between the display scan electrodes 104 and the address electrodes 107(1) to 107(M) for generating preliminary discharge at each discharge cell. Then, a pulse voltage is applied between the display electrodes 103 and the display scan electrode 104 for producing a main discharge which emits ultraviolet light at the discharge cell. The ultraviolet light excites the phosphor layer to light them. Since lighting, the discharge cells create an image in combination with not-lighted discharge cells.
The conventional PDP panel however includes the silver (Ag) electrodes where Ag may often migrate to the opposite electrodes (particularly under a high-temperature, high-moisture condition) when being energized, hence causing a short-circuit or a current leakage between terminals. It is well known that the migration of Ag under a high-temperature, high-moisture condition is accelerated when the front and back glass substrates are made of a float glass containing weight 3 to 15% of sodium (Na) or potassium (K).
FIGS. 11A and 11B illustrate electrode leads of the conventional PDP.
In a PDP of a NTSC (VGA) type shown in FIG. 11, a distance between the address electrodes 107(1) and 107(2) is substantially 160 xcexcm while a distance between the display scan electrodes 104(1) and 104(2) is substantially 500 xcexcm. High resolution PDPs for high-definition TV or SXGA format have a distance between any two adjacent electrodes being xc2xd that of the NTSC (VGA) format type. Accordingly, the intensity of an electric field between the electrodes is doubled, and the migration of Ag takes place more often in the high-definition PDP.
In addition to the Ag-migration, the float glass substrates may cause Ag to be dispersed, as Ag ion, into the substrate material or dielectric material during the baking of the Ag electrodes or the baking of the dielectric glass layers. The dispersed Ag ion can be reduced by tin (Sn) or sodium (Na) ion in the glass substrates and Na or lead (Pb) ion in the dielectric glass and thus is deposited as colloidal particles. The Ag colloidal deposition may tint the glass with yellowish color (as depicted in J. E. Shelby and J. Vitko Jr., xe2x80x9cJournal of Non Crystalline Solidsxe2x80x9d, Vol. 150 (1982), pp. 107-117), hence deteriorating a quality of an image on the panel. The yellowish Ag colloidal deposition, absorbing light of a wavelength of 400 nm, declines a luminance and a chrominance of blue color hence lowering a color temperature of the panel.
For elimination of the Ag-migration and the yellowish deposition, a technique where the sodium contained float glass with an SiO2 film is coated is proposed. However, since having a thermal expansion coefficient of 4.5xc3x9710xe2x88x926(1/xc2x0 C.), which is smaller than that of the float glass of 8.0xc3x9710xe2x88x926(1/xc2x0 C.), the SiO2 film may create cracks after the baking process. This technique is thus imperfect for eliminating the Ag-migration and the yellowish deposition. In particular, the technique is less applicable to any high-definition display panel of the high-vision format or the SXGA format.
A plasma display panel (PDP) includes a first panel having a glass substrate fabricated by a floating method and a metal oxide layer provided on said glass substrate, a second panel facing said first panel to form a discharge space between said first panel, and an electrode containing Ag provided on said first panel.
As being prevented from a migration of Ag thus reducing a yellowish color change, the PDP can be improved in both luminance and image quality.